Early dynamics of excitation and inhibition maintain late frequency tuning in auditory cortex

In the auditory cortex the onset of a tone evokes time-varying excitation and inhibition. However, the role of early inhibition in shaping the temporal properties of tone-evoked responses has not been fully characterized. By using Archaerhodopsin-3 (Arch) to photo-suppress the activity of the parvalbumin-expressing (PV) class of inhibitory interneurons, we manipulated the early component of tone-evoked inhibition. We find that early inhibition directly controls the output gain of the response, reducing the number of spikes proportionately across all frequencies. However, by controlling early activity, transient inhibition prevents late excitation and spiking for non-optimal frequencies. Thus, transient tone-evoked inhibition plays a critical long-lasting role in shaping response properties in the auditory cortex.